Tractor



Jan. 19, 1965 M. K. SHIELDS ETAL 3,156,141

TRACTOR Filed July 15, 1960 11 Sheets-Sheet 1 QMIIIIIIHIIIIIIIIIIIW EI/ MORTON K. SHIELES RUSSELL K. SHIELDS INVENTORS KENDRICK, SCHRAMM & STOLZY ATTORNEYS Jan. 19, 1965 M. K. SHIELDS ETAL 3,156,141

TRACTOR Filed July 15, 1960 ll Sheets-Sheet 2 gmmummnlh Ea. Z.

MORTON K. SHIELDS RUSSELL K. SHIELDS INVENTORS KENDRICK, SCHRAMM 81 STOLZY ATTORNEYS Jan. 19, 1965 M. K. SHIELDS ETAL TRACTOR Filed July 15, 1960 ll Sheets-Sheet 3 M mum \mil HIHIHM -N/ I i o 0 J MORTON K. SHIELDS RUSSELL K. SHIELDS ENTOR \P KENDRICK, SCHRAMM & STOLZY ATTORNEYS Jan. 19, 1965 M. K. SHIELDS ETAL TRACTOR ll Sheets-Sheet 4 Filed July 15, 1960 MORTON K. SHIELDS RUSSELL K SHIELDS INVENTORS KENDRICK, SCHRAMM & STOLZY ATTORNEYS Jan. 19, 1965 M. K. SHIELDS ETAL 3,

TRACTOR ll Sheets-Sheet 5 Filed July 15, 1960 MORTON K. SHIELDS RUSSELL K SHIELDS ,INVENTORS KENDRICK, SCHRAMM & STOLZY ATTORNEYS 1965 M. K. SHIELDS ETAL 3,

TRACTOR Filed July 15, 1960 11 Sheets-Sheet 6 49 w i 52 I06 I MORTON K. SHIELDS p RUSSELL K. SHIELDS INVENTORS KENDRICK, SCI-IRAMM & STOLZY ATTORNEYS Jan. 19, 1965 M. K. SHIELDS EI'AL 3,166,141

TRACTOR Filed July 15, 1960 11 Sheets-Sheet 7 J 94 i 90 46 I05 ki m 2 4/ 95 MORTON K. SHIELIX RUSSELL K. SHIELDS INVENTORS KENDRICK, SCHRAMM 8: STOLZY ATTORNEYS Jan. 19, 1965 M. K. SHIELDS EI'AL TRACTOR l1 Sheets-Sheet 9 Filed July 15, 1960 MORTON K. SHIELDS RUSSELL K. SHIELDS v INVENTORS KENDRIQK, SCHRAMM & STOLZY ATTORNEYS Jan. 19, 1955 M. K. SHIELDS EI'AL 3,

TRACTOR Filed July 15, 1960 11 Shee t s-Sheet 1o MORTON K. SHIELIB RUSSELL K. SHIELDS INVENTORS KENDRICK, SCHRAMM 81 STOLZY ATTORNEYS Jan. 19, 1965 M. K. SHIELDS ETAL 'mc'roa Filed July 15, 1960 11 Sheets-Sheet 1.1

MORTON K. SHIELm RUSSELL K. SHIELDS INVENTORS KENDRICK, SCHRAMM 81. STOLZY ATTORNEYS United States Patent O.

3,166,141 TRACTQR Morton K. Shields, 705i? Yolanda, lieseda, alif., and Russell K. Shields, Encino, Tali-i. (5735 Halhrent, Van Nuys, Calif.)

E-iied l5, 1%@, er. No. 43,154 1% Claims. {$3. 1891-21) The chief requirement of a tractor to be used to tow house trailers, boat trailers and airplanes is .that it must be relatively small in size. This is true not only from the standpoint of economy, but also because it frequently becomes necessary to park such vehicles under conditions such that the vehicles themselves occupy most of the available parking space and little is left in whicha tractor maybe operated.

Although the requirement that a tractor for such vehicles should be small in size would seem to be easily met by simply miniaturizing any conventional type of tractor, several difficult problems present themselves if such an attempt is made. One of these problems relates to what may be defined as primary skidand secondary skid. Briefly, primary skid is that skid produced in steering two wheels of a conventional four-wheeled vehicle in a manner such that the wheels lie generally in planes parallel to each other when the vehicle is steered into a turn. Primary skid can be eliminated by a complicated and rather heavy special steering transmission. However, secondary skid is inevitable in a-turn due to the finite tread width of the wheels.

Primary skid can be completely eliminated by using a three-wheeled tractor. However, due to the wheel base, dimensions and weight of house trailers and airplanes especially, such a small three-wheeled tractor has the dangerous tendency to tip over. i 7 Another requirement of a tractor useful for parking heavy vehicles, such as housetrailers and airplanes, is that it must be able to turn from a 90 right turn to a 90 left turn and vice versa rapidly without substantial physical eifort being involved. This means that if power is used in such a case, in order to keep the tractor small by keeping its engine small, such a turn must be possible without the need for considerable power. 7

Still another requirement for moving house trailers is the use of a four-wheeled vehicle which will not tip over even in rugged terrain;

Although to the present time no prior art tractor for towing house trailers or boat trailers'or airplanesh'as met any of the requirements set out hereinbefore, the device of the present invention does so by providing a chassis, a caster-type wheel mounted at each of the forward and rearward ends of the chassis, a driven wheel mounted on each side of the chassis, the'drivenwheel's being fixed to shafts in position to rotate in respective longtudinal planes, and power means including a mechanical differential mounted on the chassis for rotating 'tractor of the invention to tip over is eifectively eliminated by the use of four wheels.

" 'In accordance with another outstanding feature of PatentedJan. 19,19

the present invention, a universal-type or ball and socket,

trailer hitch is employed. This means that the tractor of the present invention may be turned from a right a.

turn to a 90 left turn and vice versa without substantial physical effort being involved and without the need for any mechanical power from the tractor engine'what'soever. This is true because the tractor of the present invention can be so turned without, in fact, moving a house trailer or the like which may be hitched to it at the time only the tractor is turned. Note will be taken that the mechanical differential in combination with the railer support position for the trailer hitch providesthis advantage and that both are indispensable in this one regard. In this same regard, it is to be noted that the use of auniversal-type trailer-hitch, such as a ball and socket joint, is unusually useful when employed with the tractor of the present invention where sharp turns are required and especially on rough ground.

In turning, when power is supplied to the driven wheels, 'it .is' also a feature of the present invention that each caster-type wheel mounted on .the rearward end of the chassis, a driven wheel mounted on each side of vthe chassis, the driven wheels being fixed to shafts inpositions to rotate in the respective longitudinal planes, power means including a mechanical difierential mounted on the chassis for rotating'said driven wheels, a U-shaped 1 member having legs extending rearwardly toward the driven wheels in an approximately horizontal plane, the U-shaped member having the ends of its legs mounted on the chassis to rotate about a horizontal transverse axis, a caster-type wheel suspended from the bight portion of the U-shaped' member, and means to support the forward end of the chassis movable on the bight portion of the U-shaped trn'ember. Thus, on rough ground, the front wheelof the tractor of the present invention may be adjustedyto ride over largebumps in theroad. f

In a similar regard, in accordance'with one aspect of the invention, a tractor of a construction is provided including a chassis, a caster-type wheel mounted at'each of the forward and rearward ends of the chassis, a driven It is a feature ofthe invention that a boat trailer tractor may be provided including-a chassis, a castertype wheel mounted at the forward end of thechassis,

a longitudinal member to extend rearwardly of the chassis, the longitudinal member being rotatable about its forward end, a caster-type wheel suspended from the rearward end of the. longitudinal member, and detent means on the chassis to hold the longitudinal member in a substantially horizontal "position, the detent means being releaseable to permit rotation of thechassis upwardly at its forward end about the rotationalaxis of the driven wheels. Thus, a ball of the ball and sockettype trailer hitch on the tractor of the invention may be mtated rearwardly and downwardly under th'e'socket on a boat trailer and a hitching operation accomplished rapidly and without substantial effort.

The above-described and other advantages of the trac'toi .of the presentinvehtion may be better understood from the following description considered in connection with the accompanying drawings.

attain present invention resides shown in FIG. 1;

FIG. 3 is a top plan view of the tractor of the invention shown in FIGS. 1 and2;

FIG. 4 is a sectional view of the tractor taken on the line 44 shown in FIG. 3;

FIG. 5 is a .bottom plan view of the tractor of the invention shown in FIGS. 1 to 4, inclusive;

FIGS. 6 and 7 are still other. perspective views of the tractor of the invention illustrated in FIGS. 1 to 5, in- I elusive. V

FIG. 8 is a sectional view taken on the line 88 shown in FIG. 7;

FIG. 9 is a sectional view of the tractor of the invention taken on the line '99 shown in FIG. 8;

FIG. 10 is a partly diagrammatic side elevational view of the'tractor of the invention shown in FIGS. 1 to 9, inelusive, illustrating an operational characteristic thereof;

. FIG. ll'is atop plan view of a broken-away portion of the tractor made in accordance with another embodi ment of the invention;

FIG. 12 is a sectional view of the tractor taken on the line 12--12 shownin FIG. .11;

FIG.. 13 is aside elevational view of a broken-away embodiment of the invention; FIG. 14 is a sectional view of the tractor taken 0 the line 14 14 shown in FIG. 13; and V i FIGS. 15 and 16 are perspective views of a portion of a tractor made in accordance with another invention.

In the drawing in FIG. 1, a tractor 20, made in accordance with the invention, is illustrated having a chassis 21 on which is mounted an internal combustion engine and feature of the portion of the tractor made in accordance with another clutch assembly 22 having ahousing 23. 7 Neither the internal combustion engine nor the clutch is shown in detail, both being conventional. The clutch is preferably a conventional centrifugal clutch which mechanically connects an output shaft to the internal combustion engine drive shaft upon the internal combustion engine drive shaft reaching a predetermined speed, the clutch output shaft having a sheave thereonto drive a sheave 24 fixed to an input shaft'25 to'a transmission 26 by means of V-belts 27. The internal combustion engine output shaft, the clutch output shaft, and the sheave on the clutch out putshaft are located in housing 23, all being conventional structures. A mufiler and exhaust assembly 28 is pro.- vided for the internal combustion'engine which projects through an opening 29 in'the wall of housing 23.. As shown in FIG. 2, housing 23 is provided with a cylindrical extension 30 to surround a starting rope and drum assembly, one end of. the rope being connected to a vhandle grip 31 as is conventional. r a

The throttle of the internalcombustion engine has two cables connected to it indicated at 32 and 33, whereby the throttle of the internal combustion engine. can be operated by the depressionof either one of .theright and left hand throttle buttons 34 and 35, respectively. Throttle buttons 34 and 35 are springbiased upwardly by springs 36 and 37,'respectively. 'The wires of cables 32 and 33 I are indicated at 38 and 39, respectively, in FIG. 1, the

sheaths of cables 32 and 33 being fixed relative to chassis 21 at 40 inside housing 23 and onthe lower side of cylindrical end portions 41 and 42, respectively, surrounding a horizontally disposed shaft indicated at 43 in FIG. 3 which is fixed thereto to operate the transmission 26a's will be explained hereinafter. Suflieeit at this point to say that shaft 43 is rotatably mounted inbearings 44 and 45 as shown in dotted lines inside tubular handle bar extensions to the right and left of the tractor 20 indicated at 46 and 47, respectively, in FIG. 3, extensions 46 and 47 being welded to the upper ends of tubular extensions 48 and 49, respectively, shown'in both FIGS. 1 and 5 as being bolted to chassis 21 at 50 and 51, respectively.

A lever 52 is fixed to the throttle of the internal combustion engine and is biased by a helically coiled spring 53 having its lower end fixed relative to chassis 21 so that unless buttons 34 or 35 are forceably depressed, the throttle of the combustion engine remains almost closed.

Transmission 26 simply includes a three-to-one gear reduction with a gear shift operable to drive the tractor 2t) forward or in reverse. As shown in FIG. 2, trans mission 26 has input shaft 25 projecting outwardly therefrom as well as an intermediate shaft 54 and an output shaft 55 having a sprocket 56 fixed thereto. Around sprocket 56 a chain 57 is located which also surrounds a sprocket 58 rotatable around a bushing on shaft 59 that is fixed to engine supporting framework 60, framework 60 being fixed to chassis 21. The housing of transmission is of course fixed relative to chassis 21, transmission 26 itself being conventional.

The tractor 20 of the present invention shown in FIGS. 1 and 2 is provided with front and rear caster-type mounted wheels 61 and 62, respectively, and wheels 63 and 64 on opposite sides of the tractor 20 to be driven to move the tractor. As will be apparent, wheels 63 and 64 are drivenviasprocket 58 by means of a sprocket 65 fixed to sprocket 58 shown in FIG. 4, and by a chain 66 shown in both FIGS. 3 and 4 that encompasses a sprocket 67 that is fixed to a mechanical differential indicated. generaly at 67' in FIG. 5 by meansof bolts 68 which hold .the parts of the mechanical differential 67 together. Sprocket 67 may be welded, or otherwise fixed, in any convenient manner to one-half of the housing of differential 67' indicated at 69, which is bolted to another half 79 by means of bolts 68. Chassis 21 is slotted at 151' as shown in FIG. 3 and 4 to accommodate sprocket 6 7 v and chain 66 engaged therewith to pass from the position around sprocket 65 above chassis 21 to a position around sprocket 67 below chassis 21. A web 155 is provided '7 approximately at the center of the chassis 21 for strength as shown in FIG. 5. Differential 67' is provided'with output shafts, 717and 72, respectively, fixed to wheels 63 ears82 welded to chassis 21 at 83. Boltscan also be seen in FIG. 5. Since framework 6t? is rotatable about the pin 77, the horizontal position-thereof may be adjusted by means of rotation of a nut 84 whichrests on top of a hollow cylindrical body 85 that is pivoted at its lower end about a horizontal axis 86, the hollow passageway inside body 85 being adapted to .take the lower threaded end of a shaped rod 87 having an upper end at 88 rotatable in a hole through the framework 60.

The gear shift of transmissionlfi is operated by'movinga shaft 89 extending horizontally therein to the right or left, as viewed from the rear of the tractor 20. A movement of shaft 89 is, made by rotating pipes 90 or-9 1 to the forward or to the rear approximately 45, pipes 90 and 91 being fixed to end portions 41 and 42, respectively, of the handle bar arrangementwhieh are, in turn, fixed to shaft 43as shown in FIGS. Rotation of shaft 43 rotates an arm-92 that is fixed thereto bymeansofafset screw. 93 to move a rod 94 shown in both FIGS. 1 and. 3 approximately vertically upwardly or downwardly, de-

pending upon the direction of rotation of pipes 91 and 92.

Pipes 99 and 91 are hollow to permit thewires 38 and into the corresponding sheaths thereof, respectively; Rod 94 operates shaft 89 through a lever 95, rod 94 being pivoted at its lower end through a hole through one end of lever d5, a bolt 6 being employed to rotatably mount a block 97 about the other end of lever 95, bolt 96 also holding block 97 in a fixed axial position on shaft 89. A bolt 98 is provided through the corner of lever 95 to maintain it in a position rotatable about bolt 980:1 a bracket 99 which is, in turn, bolted at 196 to a projection 1511 Welded to member 48. This arrangement is shown in both FIGS. 1 and 3.

As shown in FIG. 3, levers 1&2 and 193 are provided which are maintained in fixed axial positions on shaft 43 although rotatable therearound by means of corresponding set screws 194 and H35, respectively, rotatable in grooves, not shown, in shaft 43. Rotation of levers 192 and 103 independently brake corresponding driven wheels 63 and 64 by operating corresponding brake cables 1% and 1&7, respectively, shown in FIG. 1.

Another outstanding feature of the invention resides in the use of a universal-type or ball and socket trailer hitch 108 including a ball 16? fixed to a shaft 11% which is threaded into a framework 111 welded to chassis 21. Rotation of shaft 116 is prevented by means of a pin 112 which projects through an appropriate hole in framework ill and in one of several holes 113 in shaft 11% as shown in PEG. 6. Framework 111 is slotted at 152, as shown in FIGS. 4 and 6, to accommodate sprockets 67 and chain 66.

The socket of'the trailer hitch 108 indicated at 114 is incorporated integrally with the forward end of a house trailer indicated at 115, most of which is broken away. House trailer 115 is provided with a conventional jack 116 to lift the socket 134 of trailer hitch 1% above the ball 1th? in order that the tractor may be moved rearwardly so that the ball 109 lies immediately below socket 114. In this case, jack 116 can be operated to lower the trailer 115 until the lower end of the jack 116 rises from the ground and socket 114 rests on top of the ball 10?.

t will be noted that in accordance with an outstanding feature of the invention, ball 169 is located in a vertical plane through the rotational axis of wheels 63 and 64 midway between them. The same will be appreciated from the views illustrated in FIGS. 3 and 8 when taken together. A construction line 117 has been added in FIG. 8 to illustrate this fact, construction line 117 passing through the center of shaft 11% and through the axis of shaft 72 to which wheel 64 is fixed. From FIG. 5, it will be apparent that both shafts 71 and 72, to which wheels 63 and 64- respectively are fixed, have an identical horizontal rotational axis.

Still another outstanding feature of the invention is the use of a U-shaped member 118, perhaps best shown in FIGS. 1, 3 and 6, which is mounted to rotate about bolts 119 which project through ears 129 that are Welded to chassis 21. Bolts 11% have a common horizontal axis which must be parallel to the rotational axis of wheels 63-and 64. This orientation can be observed from FIGS. 3, 4, 5, 8 and 10. U-shaped member 118 extends generally in a horizontal plane, although it rotates through relatively small angles with respect thereto about bolts 119 and has a bottom or bight portion at the forward end of the tractor 29 to support chassis 21 thereon through an arrangement perhaps best shown in FIGS. 8 and 9.

Front caster-type wheel 61 is rotatable about an approximately vertical pin 121 that is held in position by a plate 122 Welded to the bottom of U-shaped member 118. As shown in FIGS. 1 and 8, front caster-type wheel 61 is not only rotatable about a substantially horizontal axle 141 located through a pair of plates 142 and 143 to which a top plate 144 is welded to provide a fork but also rotatable about pin 121 which is substantially vertical. Plate 145 is bolted to plate 122 by means of bolts 145 shown in both FIGS. 8 and 9. Bolts 146 are also shown in FIG. 5. Between plates 144 and 145, a bushing 147 is provided. Plate 122 maybe welded to plate 145 if desired, thus, if an end plate portion, indicated at 148 in FIG. 8, is welded tothe lower end of pin 12 1, wheel 61 cannot come loose fromthe U-shapedmember 118.

A portion of the weight of chassis 21 is actually supported on wheel- 61 through threads 123 on a shaft 124 that is rotatable by handle 125. Shaft 124is threaded into a square out 126 supported in the channel of a bracket 127 that is, in turn, welded'to members 48 and 49,

which, it will be recalled, are bolted to chassis 21 at and 51. Nut 12.5 isroundedat'its'upper end to permit it to rock in bracket 127. A portion of the weight of chassis 21 is then supported on a helically coiled'spring 23 at a plate 129 located on top thereof between-the top of the spring 123 and a shoulder 13% on shaft 124, plate 129 having a hole 131 therethr-ough through which an extension 132 of shaft 124 projectsand is slidable in a bearing 133 located in a pipe extension 134 that is welded to bracket 135, perhaps best shown in FIG. 9 A ring 149 is also welded to bracket 135 to contain the lower end of spring 123, a set screw 159 being threaded through ring 149 to maintain the lower end of spring 123 in'place' against bracket 135. a

Bracket 135 is rotatable about bolts 136 and 137 which project therethroughand through corresponding ears 138 and 139 welded to U-shaped member-118 and to plate 122 which is also welded thereto. 'The rocking action of U- shaped member 118'about bolts 13d and 1373s permitted in order that shaft 124 can rotate when U-shaped member 1T8 does so. V

In accordance with an outstanding feature of the invention, the operation of the'U-shaped member 113 is as illustrated in FIG. 10 wherein shaft 124is rotated by handle 125 to lift rear caster-type Wheel 62 upwardly. This is permitted in accordance with the invention because it is necessary to provide this feature to take the tractor 20 over rough ground. It will be evident from a comparison of FIGS. 8 and 10 that U-shaped member 118 is ata substantially greater angle with respect to the horizontal in PK}. 10 than in FIG. 8.

Rear caster-type wheel 62 is mounted identically with 7 front caster-type wheel 61. As a matter of fact, structures 141, 142, 143, 144, and 146 incorporated in mounting front caster-type wheel 61 may be identical to the structures indicated at 141, 142', 143, 144, 145' and and 146, respectively, illustrated in FIGS. 1 and 10. The same. is :true of the identity of structures 121, 147- and 148 to mount rear caster-type wheel 63 asregards structures121, 147 and 148 employed to mount front castertypewheel 61 as'shown in FIG. 4. A beam 122 has its forward end fixed to chassis 21 by means of a pair of bolts 76 employed in mounting one of the bearings 74 shown in FIG. 5 thereto. Member 122' serves the same pur pose as plate 122' perhaps best shown in FIG. 8 in mounting front caster-type wheel 61; Thus,- it is to be noted that not only is the front-wheel 61 a caster-type wheel, but also the rear wheel 62.

As shown in FIGS. 5, 6, 7 and 8, right and left brake springs 153'and 154 are employed to bias the brakes ,of corresponding wheels 63 and 64 to a deactuated position, one end of the springs 153 and 154 being connected to the brakes of'corresponding wheels 63 and 64 and the other end of springs153 and 154 being connected to chassis 21. V

A modification of the invention is shown in. FIG. 11.

The remainder of the tractor, not shown, may be iden-' tical to that illustrated in FIGS. 1 to 10, inclusive. Many of the structures shown in FIG. 11 may also be identical to those shown inFIGS. 1 to 10, inclusive. In the first place, a sprocket 58 is shown which may be identical to sprocket 58 shown in FIG. 2. Apair of driven wheels 63 and 64' are also provided in FIG. 11 which may be identical to Wheels 63 and 64, the difference being in the drive to wheels 63' and 64. The embodiment of the invention shown in FIG. 11 is adapted to take the nose wheel of the tricycle landing gear airplane in a slot 156 i 157 and 158 through chains operate sprockets 159 and 160, respectively, which are fixed to shafts 161 and 162, respectively, connected to driven wheels 63" and 64'.

Mechanical differential output shafts 71' and 72' are maintained in a fixed axial, but rotatable, angular position by means of corresponding bearings 163 and 164. The shafts to which wheels 63 and 64' are fixed, that is, shafts 161 and 162, are maintained in fixed axial, but rotatable angular positions in bearings 165 and 166 respectively by means of pins 167 and 168 through shafts 161 and 162, respectively.

Additionally, means are provided on chassis 21 to lift the nose wheel of the airplane off of. the ground. This means includes a jack 169, as shown .in FIG. 12, which is provided with a handle 170 to rotate a shaft 171 that is threaded through a plate 172 that is hinged to chassis 21 at 173, the hinge including a plate 174 welded to chassis 21. Thus, the lower end of shaft 121 lifts plate 172 from chassis 21. A tubular member 175 is. welded to plate 172. Tubular member 175 has inwardly turned ends 176 and 177 at the rearward end of its legs. The nose wheel axle of airplanes conventionally have a hollow. internal passageway into which projections 176 and 177 .may be fitted by springing legs of U-shaped member 175 apart. Alternatively, screw threaded means, similar to jack 69 may be employed, such means extending. trans- -versely through ears fixed to the opposite legs of U- .shaped member 175. .Such screw threaded means 'may be employed to adjust the transverse position of ends 176 and 177 until they are spread far enough apart to ac commodate the ends of the nose wheel axle and subse' quenly to be closed into a position internally thereof.

Still another embodiment of the inventionis illustrated in FIGS. 13 and 14. Those portions of the tractor omitted may be identical to that shown in FIGS. 1 to. 10, inclusive. The only modification is the mountingof member 122. A member 122'" may be identical to member 122' but for the means for mounting it to a chassis 21" which may be identical to chassis 21. This means includes a pair of cars 178 welded to chassis 21", a pair of ears 179 welded to. member 122" and a belt 180 through each of the four ears 178 and 179 as indicated in both FIGS. .13 and 14. In this manner, member 122". is rotatable about the bolt 180 with respect to chassis 21", whereby chassis 21" may be rotated upwardly and rearwardly about axle 71 and 72 of wheels 63 and 64, respectively, to place ball 109 of trailer hitch 108 under socket 114 of trailer 115 without the necessity of raising the trailer 115 by means of jack 116. The'same is, useful in handling boat trailers in which tractor 20 of the present invention may be made .very small.

The rotatable character of member 122" is indicated in dotted lines at 122"" in FIG. 13. A book 181 is provided in FIG. 13 to maintain member 122" in a fixed horizontal position parallel to that of chassis 21" when it is not desired that the tractor of the invention be rotated as explained in the immediately preceding paragraph. Hook 1811is rotatable about a pin 182 which extends through an ear 183 welded to chass-is'21".- An angle stop bracket for hook 181 is provided at 184. Hook 181 is biased rearwardly by means of a coil spring 185. .Due to the shape of hook 181, the member 122 is stable in either of its hooked or unhooked positions. That'is, if member 122" is maintained in a position shown in solid lines in FIG. 13 by hook 181, the same will not become unhooked due to bias action of spring 185. Still further, the bias action of spring 185 with stop 184 and the particular shape of the lower end of hook 181 will prevent 8 member 122" from being hooked when it is unhooked as indicated in the dotted lines 122"" shown in FIG. 13.

From the foregoing, it will be appreciated that the primary skid described hereinbefore attendant upon the rotation of two dirigible wheels of a conventional four-wheeled vehicle about vertical axes in planes parallel to each other is completely avoided by the use of front and rear castertype wheels 61 and 62 inaccordance withthe present invention with the pair of wheels-63 and 64 driven by a conventional mechanical differential 67. However, although primary skid is avoided in accordance with the tractor 20 of the invention, the tendency of the tractor. 20 to tip over is effectively eliminated by useof the four wheels 61, 62, 63 and 64, rather than three wheels.

In accordance with another outstanding feature of the present invention, the universal-type, that is, ball and socket trailer hitch 108 is employed." This means that the tractor 20 may be employed to turn from a right turn to a 90 left turn and vice versa without substantial physical effort being involved, and without the need for any mechanical power from the tractor engine in housing 23. This is true because the tractor 20v can be so turned without, in fact, moving house trailer which may be hitched to it. The trailer 115 may, in fact, be hitched to the tractor 20 when the tractor is turned 180, and still no substantial physical effort is involved in turning the tractor 20 manually. Note will be taken that the mechanical differential 67' in combination with the particular support position of trailer hitch knob 109 on framework 111 fixed to chassis 21 provides this unusual ease in turning advantage, both mechanical differential 67 on the trailer support position of knob 109 directly above the common axis of rotation of driven wheels 63 and 64' in a vertical plane midway between them being indispensable in this one regard. In the same regard, it is to be noted that use of the universal-type trailer hitch 108 is unusually useful when employed with tractor 20 of the present invention where sharp turns are required, and especially on rough ground.

In turning, when power is supplied to driven wheels 63 and 64, it is also a feature of the invention that each one of the driven wheels 63 and 64 may be braked independently by operation of levers 102 and 103 corresponding respectively thereto. The use of the same further increases ease of steering.

According to an aspect of the invention, the tractor 20 of the invention is unusually useful in employing the combination of chassis 21, caster-type wheels 62, and driven wheels 63 and 64 mounted on each side of the chassis 21. The driven Wheels are fixed to shafts 71 and 72 respectively in positions to rotate in respective longitudinal planes. When power means, including the internal combustion engine in housing 23, are employed, including mechanical differential 67 mounted on chassis '21 for rotating driven wheels 63 and 64 and U-shaped member 118 is additional provided having legs extending rearwardly toward driven wheels 63 and 64 in an approximately horizontal plane, the U-shaped member 118 can rotate about its ends and about the axes of bolts 119. Thus, by suspending front caster-type wheels 61 from the bight or bottom portion of U-shaped member 118 at the front of the tractor 20, and providing means including shaft 124 and nut 126 to support the forward end of chassis 121 movably on the bight portion of U-shaped member 118, on rough ground, the height of front wheel 61 may be adjusted by rotation of shaft 124 by means of handle to ride higher than the driven wheels 63 and 64 with rear caster-type wheel 62 and the tractor 20 will thereby ride over large bumps in the road. 7

Notwithstanding the fact that the embodiment of the invention shown in FIG. 11 is different from that shown in FIGS. 1 to 10, inclusive, in certain respects, it is still to be noted that the forward end of an airplane will be supported substantially in a vertical plane through the axes of shafts 161 and 162, as indicated at dotted line 186 in FIG. 12. This means that the advantage of the present invention overcoming primary skid and ease in turning is maintained. It is to be noted that the support of a nose wheel of a tricycle landing gear airplane is also universaltype trailer bitch and is defined as the same for use hereinbefore and hereinafter, including its specific use in the claims because the nose wheel of the tricycle landing gear airplane is not only rotatable about a horizontal axis, but also about the vertical axis of the strut from which it is suspended.

Still another feature of the invention resides in the use of the alternative mounting embodiment of FIGS. 13 and 14 in which member 122" is rotatable about the bolt 180. Bolt 180 is maintained in a fixed position relative to chassis 21", whereby a speedy and efficient connection between trailer hitch knob 109 and socket 114 on a boat trailer may be made. This can'be performed by manually unhooking hook 181 from the forward end of member 122", lifting the tractor to make it rotate upwardly and rearwardly at the front thereof about the axes of wheels 63 and 64. The tractor is then moved rearwardly until the ball of the trailer hitch lies directly beneath the socket thereof.

It is well known that the housing of differential 57' may be locked to chassis 21 to provide a parking brake.

Shaft 119 of 6 may be smooth and hydraulic or tractor 15A are shown at 15B and 15C. A member 15D is fixed to a chassis 15E of tractor 15A to support a caster-type wheel rearwardly of the chassis 15E. A ball 15F of a ball-and-socket type trailer hitch is mounted on a framework 156 that is rotatable by a bolt 15H that extends through the bottom of framework 156 and through a pair of ears 15I welded to chassis 15E. A handle 15'] is welded to framework 156 to rotate the same upwardly and rearwardly.

Handle 151 is maintained in a fixed position on top of chassis 15E by means of a hook 15K which has a handle 15L fixed thereto. Hook 15K is rotatable with respect to chassis 1513 on apin 15M fixed to chassis HE. A stop 158 is also fixed to chassis 15E to prevent rotation of hook 15K to the left as viewed in FIG. 15 when handle 15] is rotated to a position as shown in FIG. 16. A spring 150 has one end fixed to chassis 1515 and another end fixed to the lower end of hook 15K to maintain the portion of hook 15K beneath pin 15M against stop 15N. Handle 15] is rotated to the position shown in FIG. 16 by first rotating hook 15K to the right as viewed in FIG. 15 until hook 15K clears handle 15]. As best shown in FIG. 16, a U-shaped channel 15F is welded to chassis 15E at its lower end to support framework 156 immediately below a front portion of a square metal plate 15Q of framework 156.

Thus in the operation of the embodiment of the invention shown in FIGS. 15 and 16, framework 156 is rotated to the position shown in FIG. 16 and tractor 15A is moved rearwardly until the socket of a ball-and-socket type trailer hitch lies approximately above ball 15F Handle 15! is then pushed downwardly to the position shown in FIG. 15 to lift the trailer by engagement of the ball 15F with the socket of the trailer hitch.

From the foregoing, it will be appreciated that although only a few specific embodiments have been shown and described, many changes and modifications will, of course, suggest themselves to those skilled in the art. Hence, the invention is not to be limited to the specific embodiments illustrated, the true scope thereof being efined only in the appended claims.

What is claimed is: 1. A tractor for towing a vehicle, said tractor comprising: a chassis; a driven wheel mounted on each side of said chassis, said driven wheel being mounted'in a position to rotate about the samehorizontal transverse axis in parallel vertical planes; power means including a mechanical differential mounted on said chassis for rotating said driven wheels; and means to support a vehicle to be towed at a point in a vertical plane through'the rotational axis of said driven wheels equidistant therefrom.

'2. A tractor for towing a vehicle, said tractor comprising: a chassis; a driven wheel mounted on each side of said chassis, said driven wheels being mounted in a position to rotate about the same horizontal transverse axis in parallel vertical planes; power means including a mechanical differential mounted on said chassis for rotating said driven wheels; and a universal-type trailer hitch mounted on said chassis at a point in a vertical plane through the rotational axis of said driven Wheels equidistant therefrom.

3. A tractor for towing a vehicle, said tractor comprising: a chassis; a driven wheel mounted on each side of said chassis, said driven wheels being mounted in a position to rotate about the same horizontal transverse axis in parallel vertical planes; power means including a mechanical difierential mounted on said chassis for rotating said driven wheels; and a ball and socket type trailer hitch mounted on said chassis at a point in a vertical plane through the rotational axis of said driven wheels equidistant therefrom.

4. A tractor for towing a vehicle, said tractor comprising: a chassis; a driven wheel mounted on each side of said chassis, said driven wheels being mounted in a position to rotate about the same horizontal transverse axis in parallel vertical planes; power means including a mechanical differential mounted on said chassis for rotating said driven wheels; and a ball of a ball and socket type trailer hitch mounted on said chassis at a point in a vertical plane through the rotational axis of said driven wheels equidistant therefrom.

5. A tractor comprising: a chassis; a first caster-type wheel'mounted on one end of said chassis; a driven wheel mounted on each side of said chassis, said driven wheels being fixed to shafts in positions to rotate in respective longitudinal planes; power means including a mechanical differential mounted on said chassis for rotating said driven wheels; a u-shaped'mernber having legs extending toward both said first caster-type wheel and said driven wheels in an approximately horizontal plane, said U-shaped member having the ends of its legs mounted on said chassis to rotate about a horizontal transverse axis; a second caster-type wheel suspended from the bight portion of said U-shaped member; and means to adjust the position of the other end of said chassis relative to the bight portion of said U-shaped member.

6. A tractor comprising: a chassis; a first caster-type wheel mounted on one end of said chassis; a driven Wheel mounted on each side of said chassis, said driven Wheels being fixed to shafts in positions to rotate in respective longitudinal planes; power means including a mechanical differential mounted on said chassis for rotating said driven wheels; a U-shaped member having legs extending toward both said first caster-type wheel and said driven wheels in an approximately horizontal plane,.said U-shaped member having the ends of its legs mounted on said chassis to rotate about a horizontal transverse-axis; a second caster-type wheel suspended from the bight portion of said U-shaped member; a spring resting on top of the bight portion of said U-shaped member; and means between the other end of said chassis and the top of said spring to adjust the heightof said forward end relative to said spring.

7. A tractor comprising: a chassis; a first caster-type wheel mounted on one end of said chassis; a driven wheel mounted on each side of said chassis, said driven wheels of the bight portion of said U-shaped member; and screw threaded means to support the otherend of said chassis adjustably on the top of said spring. 7

8. A tractorfor towing a'vehicle, said tractor comprising: a chassis; a driven wheel mounted on each side of said chassis, said driven wheels being mounted in a position to rotate about the same horizontal transverse axis in parallel vertical planes; power means including .a mechanical diflerential mounted on said chassis for rotating said driven wheels; a trailer hitch member rotatable on said chassis from a'lower position under a mating hitch'member on a trailer to an upper position in a vertical plane through the rotational axis of said driven wheels equidistant therefrom; a lever arm longer than said hitch member fixed rigidly thereto; and releaseable means to hold said trailer hitch member in a substantially fixed position relative to said chassis.

9. A tractor for towing a vehicle, said tractor comprising: a chassis; a driven wheel mounted on each side of said chassis, said driven wheels being mounted in a position to rotate about the same horizontal transverse axis in parallel vertical planes; power means including a mechanical dilferential mounted on said chassis for rotating said driven wheels; a framework including a ball of a ball and socket trailer hitch rotatable on said chassis from a lower position under a socket on a trailer to an. upper position in said socket in a vertical plane through the rotational axis of said driven wheels equidistant therefrom; a leverarm longer than said hitch member rigidly fixed thereto in a position extending approximately perpendicularly thereto; and releaseable 12 means to hold said framework in a substantially fixed position relative to said chassis.

10..A tractor for towing a vehicle, said tractor comprising: a chassis; a driven wheel mounted on each side of said chassis, said driven wheels being mounted in a position to rotate about the same horizontal transverse axis in parallel vertical planes; power means including a mechanical differential mounted on said chassis for rotating said driven Wheels; means to support a vehicle to be towed at a point in a vertical plane through the'rotational axisof said driven wheels equidistant therefrom; a first caster-type wheel to support said chassis located in a position spaced from said vertical plane through the rotational axis of said driven wheels on one side thereof and a second castentype wheel'to support said chassis located in a position spaced from'said vertical plane through the rotational axis of said driven wheels on the other side thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,262,806 .Kemble Apr. 16, 1918 1,348,568 Kemble Aug. 3, 1920 1,534,329 Sargent g Apr. 21, 1925 1,567,380 Noelting et al Dec. 29, 1925 1,823,657 Lackey Sept. 15, 1931 2,145,188 Morris Jan. 24, 1939 2,329,372 Hitch Sept. 14, 1943 2,448,119 Peterson Aug. 31, 1948 2,484,951 Kubo Oct. 18, 1949 2,491,824 McKee Dec. 20, 1949 2,533,549 Bell Dec. 12, 1950 2,568,261 Stade Sept. 18, 1951 2,715,535 Prowinsky Aug. 16, 1955 2,753,192 Davis July 3, 1956 2,851,179 Vance Sept. 9, 1958 2,872,213 Hosford -2 Feb. 3, 1959 2,893,019 Renfroe et al. July 7, 1959 2,911,233 Riddle Nov. 3, 1959 2,944,836 Matthews July 12, 1960 3,049,253

Cabral Aug. 14, 

5. A TRACTOR COMPRISING: A CHASSIS; A FIRST CASTER-TYPE WHEEL MOUNTED ON ONE END OF SAID CHASSIS; A DRIVEN WHEEL MOUNTED ON EACH SIDE OF SAID CHASSIS, SAID DRIVEN WHEELS BEING FIXED TO SHAFTS IN POSITIONS TO ROTATE IN RESPECTIVE LONGITUDINAL PLANES; POWER MEANS INCLUDING A MECHANICAL DIFFERENTIAL MOUNTED ON SAID CHASSIS FOR ROTATING SAID DRIVEN WHEELS; A U-SHAPED MEMBER HAVING LEGS EXTENDING TOWARD BOTH SAID FIRST CASTER-TYPE WHEEL AND SAID DRIVEN WHEELS IN AN APPROXIMATELY HORIZONTAL PLANE, SAID U-SHAPED MEMBER HAVING THE ENDS OF ITS LEGS MOUNTED ON SAID CHASSIS TO ROTATE ABOUT A HORIZONTAL TRANSVERSE AXIS; A SECOND CASTER-TYPE WHEEL SUSPENDED FROM THE 